System for determining target misalignment in turbine shaft and related method

ABSTRACT

Systems and devices configured to determine misalignment of targets of a rotating shaft by monitoring axial and radial aspects of targets and the shaft. In one embodiment, a target monitoring system includes a first horizontal probe communicatively connected to at least one first horizontal target connected to the shaft, and a first axial probe located adjacent to the first horizontal probe and communicatively connected to the first horizontal target. The system also includes a second horizontal probe communicatively connected to at least one second horizontal target connected to the shaft, and a second axial probe located adjacent to the second horizontal probe and communicatively connected to the second horizontal target. The system may further include an end probe disposed proximate a first end of the shaft for monitoring axial movement of the shaft, and a computing device communicatively connected to the end probe and each horizontal and axial probe.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to a system for determiningtorsional displacement of a rotating shaft, and, more specifically, to asystem and method for determining movement of a power generation systemshaft and/or targets during operation.

Some power plant systems, for example certain nuclear, simple cycle, andcombined cycle power plant systems, employ turbines in their design andoperation. Some of these turbines include shafts which during operationare rotated at high speeds to transfer torque about the turbine andpower generation system (e.g., from prime drivers to generators). Theseshafts may have long axial dimensions relative to respectivethicknesses/radial dimensions of the shaft. As a result of these longaxial dimensions and the magnitude of the torque transferred, theseshafts may experience torsional displacement which may cause a first endof any given shaft to be displaced/twisted, and/or radially shiftedrelative to a second end of the shaft during operation. In some powergeneration systems the power output of turbines may be determined bymonitoring a set of targets disposed circumferentially about the shaft,the displacement of these targets relative to one another providing ameasurement of the twist imposed on the shaft due to torque on theshaft. When errors caused by radial movement are eliminated, the angleof twist on the shaft can be determined and related to a calibration. Asa result, known, controlled and measured forces are applied to theshaft, and a highly accurate measure of the associated power output ofthe turbine may be delivered. Employment of a method that includesdisposing a plurality of sensors at each end about the shaft incommunication with a set of a plurality of targets disposed about eachend of the shaft allows determination of the aforementioned error inmeasurement due to radial motion of the shaft. However, these systemsmay not be able to monitor axial shaft movement and/or may not be ableto determine the effects of the shaft movement on the accuracy of torquemeasurements. Additionally, if the targets are not parallel to acenterline of the shaft, the measurement may introduce another errorinto the measured angle of twist of the shaft which may limit processaccuracy and thus reduce the accuracy of the torque and power outputdeterminations.

BRIEF DESCRIPTION OF THE INVENTION

Systems and devices configured to monitor displacement of a rotatingshaft by monitoring axial and radial targets are disclosed.

A first aspect of the invention includes a target monitoring systemhaving: a first horizontal probe located radially outboard of a shaftand communicatively connected to at least one first horizontal targetconnected to the shaft, the at least one first horizontal targetdisposed proximate a first end of the shaft; a first axial probe locatedaxially adjacent to the first horizontal probe and communicativelyconnected to the at least one first horizontal target; a secondhorizontal probe located radially outboard of the shaft communicativelyconnected to at least one second horizontal target connected to theshaft, the at least one second horizontal target disposed proximate asecond end of the shaft; a second axial probe located axially adjacentto the second horizontal probe and communicatively connected to the atleast one second horizontal target; an end probe disposed proximate thefirst end of the shaft, the end probe configured to monitor axialmovement of the shaft; and a computing device communicatively connectedto the end probe and each of the first horizontal probe, the first axialprobe, the second horizontal probe, and the second axial probe, whereinthe computing device configured to: determine a first gradient for theat least one first horizontal target based on a displacement between thefirst horizontal probe and the at least one first horizontal target andthe first axial probe and the at least one first horizontal target; anddetermine a second gradient for the at least one second horizontaltarget based on a displacement between the second horizontal probe andthe at least one second horizontal target and the second axial probe andthe at least one second horizontal target.

A second aspect of the invention includes a method including:determining a first primary displacement between a first horizontalprobe and at least one first target on a shaft, the at least one firsttarget located proximate a first end of the shaft; determining a secondprimary displacement between a first axial probe and the at least onefirst target; calculating a first gradient of the at least one firsttarget based on the first primary displacement and the second primarydisplacement; monitoring axial movement of the shaft via an end probe;and determining an amount of false twisting of the shaft at loadcondition based on: a difference between the first gradient and acalculated second gradient; and the axial movement of the shaft.

A third aspect of the invention includes a turbine having: a stator; aworking fluid passage substantially surrounded by the stator; and ashaft configured radially inboard of the stator and in the working fluidpassage; and a target monitoring system communicatively connected to theshaft and configured to monitor displacement of the shaft duringoperation of the turbine, the target monitoring system including: afirst horizontal probe located radially outboard of the shaft andcommunicatively connected to at least one first horizontal targetconnected to the shaft, the at least one first horizontal targetdisposed proximate a first end of the shaft; a first axial probe locatedaxially adjacent to the first horizontal probe and communicativelyconnected to the at least one first horizontal target; a secondhorizontal probe located radially outboard of the shaft communicativelyconnected to at least one second horizontal target connected to theshaft, the at least one second horizontal target disposed proximate asecond end of the shaft; a second axial probe located axially adjacentto the second horizontal probe and communicatively connected to the atleast one second horizontal target; an end probe disposed proximate thefirst end of the shaft, the end probe configured to monitor axialmovement of the shaft; and a computing device communicatively connectedto the end probe and each of the first horizontal probe, the first axialprobe, the second horizontal probe, and the second axial probe, whereinthe computing device configured to: determine a first gradient for theat least one first horizontal target based on a displacement between thefirst horizontal probe and the at least one first horizontal target andthe first axial probe and the at least one first horizontal target; anddetermine a second gradient for the at least one second horizontaltarget based on a displacement between the second horizontal probe andthe at least one second horizontal target and the second axial probe andthe at least one second horizontal target.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this invention will be more readilyunderstood from the following detailed description of the variousaspects of the invention taken in conjunction with the accompanyingdrawings that depict various embodiments of the invention, in which:

FIG. 1 shows a three-dimensional partial cut-away perspective view of aportion of a turbine according to an embodiment of the invention;

FIG. 2 shows a cross-sectional view of a rotating shaft in a simplecycle power generation system in accordance with embodiments of theinvention;

FIG. 3 shows a cross-sectional view of a rotating shaft in a combinedcycle power generation system in accordance with embodiments of theinvention;

FIG. 4 shows a perspective view of the combined cycle power generationsystem of FIG. 2 in accordance with embodiments of the invention;

FIG. 5 shows a cross-sectional view of a rotating shaft taken along viewline 7-7 of FIG. 2 or 3 according to an embodiment of the invention;

FIG. 6 shows a cross-sectional view of a rotating shaft taken along viewline 7-7 of FIG. 2 or 3 including a graphical representation of targetdisplacement by shaft movement according to embodiments of theinvention;

FIG. 7 shows a schematic view of a target monitoring system inaccordance with embodiments of the invention;

FIG. 8 shows a schematic illustration of an environment including acontrol system in accordance with an embodiment of the invention;

FIG. 9 shows a schematic block diagram illustrating portions of acombined cycle power plant system according to embodiments of theinvention; and

FIG. 10 shows a schematic block diagram illustrating portions of asingle-shaft combined cycle power plant system according to embodimentsof the invention.

It is noted that the drawings of the invention are not necessarily toscale. The drawings are intended to depict only typical aspects of theinvention, and therefore should not be considered as limiting the scopeof the invention. It is understood that elements similarly numberedbetween the FIGURES may be substantially similar as described withreference to one another. Further, in embodiments shown and describedwith reference to FIGS. 1-10, like numbering may represent likeelements. Redundant explanation of these elements has been omitted forclarity. Finally, it is understood that the components of FIGS. 1-10 andtheir accompanying descriptions may be applied to any embodimentdescribed herein.

DETAILED DESCRIPTION OF THE INVENTION

Aspects of the invention provide for a target monitoring system whichincludes an end probe (e.g., a Bentley Nevada probe, clearance probe, aproximity probe, a magnetic pick-up sensor, etc.) configured todetermine axial movement of a rotating shaft and a set of axial probesconfigured to determine the gradient of misalignment for each target bymonitoring changes in the displacement of each target disposed on theshaft.

In contrast to conventional approaches, aspects of the invention includean end probe and a set of axial probes which are disposed proximate setsof horizontal and vertical probes and configured to monitor a set oftargets on the shaft. During operation the target monitoring systemmonitors the displacement of the set of targets relative to at least oneof an axial probe and a horizontal and/or vertical probe to determine agradient of misalignment for each target. An end probe monitors axialmovement of the shaft itself during operation, and the system is able todetermine the amount of false twisting of the rotating shaft byconsidering the product of the gradient and the axial movement, andincorporating this false twisting into the torque and/or power outputcalculation for correction.

As used herein, the terms “axial” and/or “axially” refer to the relativeposition/direction of objects along axis A, which is substantiallyparallel to the axis of rotation of the turbomachine (in particular, therotor section). As further used herein, the terms “radial” and/or“radially” refer to the relative position/direction of objects alongaxis (r), which is substantially perpendicular with axis A andintersects axis A at only one location. Additionally, the terms“circumferential” and/or “circumferentially” refer to the relativeposition/direction of objects along a circumference which surrounds axisA but does not intersect the axis A at any location.

Turning to the FIGURES, embodiments of systems and devices are shown,which are configured to determine torsional displacement of a rotatingshaft including axial displacements of the shaft during operation bymonitoring a set of targets disposed about the shaft with a set ofprobes. Each of the components in the FIGURES may be connected viaconventional means, e.g., via a common conduit or other known means asis indicated in FIGS. 1-10. Referring to the drawings, FIG. 1 shows aperspective partial cut-away illustration of a gas or steam turbine 2.Turbine 2 includes a rotor 4 that includes a rotating shaft 20 and aplurality of axially spaced rotor wheels 8. A plurality of rotatingblades 80 are mechanically coupled to each rotor wheel 8. Morespecifically, blades 80 are arranged in rows that extendcircumferentially around each rotor wheel 8. A plurality of stationaryvanes 82 extend circumferentially around shaft 20, and the vanes areaxially positioned between adjacent rows of blades 80. Stationary vanes82 cooperate with blades 80 to form a stage and to define a portion of aflow path through turbine 2.

In operation, gas 84 enters an inlet 86 of turbine 2 and is channeledthrough stationary vanes 82. Vanes 82 direct gas 84 against blades 80.Gas 84 passes through the remaining stages imparting a force on blades80 causing shaft 20 to rotate. At least one end of turbine 2 may extendaxially away from rotating shaft 20 and may be attached to a load ormachinery (not shown) such as, but not limited to, a generator, and/oranother turbine.

In one embodiment, turbine 2 may include five stages. The five stagesare referred to as L0, L1, L2, L3 and L4. Stage L4 is the first stageand is the smallest (in a radial direction) of the five stages. Stage L3is the second stage and is the next stage in an axial direction. StageL2 is the third stage and is shown in the middle of the five stages.Stage L1 is the fourth and next-to-last stage. Stage L0 is the laststage and is the largest (in a radial direction). It is to be understoodthat five stages are shown as one example only, and each turbine mayhave more or less than five stages. Also, as will be described herein,the teachings of the invention do not require a multiple stage turbine.

Turning to FIG. 2, a cross-sectional view of a portion of a targetmonitoring system 200 connected to a shaft 20 while a torque 27 isacting on shaft 20 that serves as a load coupling shaft is shownaccording to embodiments of the invention. Target monitoring system 200includes a first axial probe 212 located proximate a first horizontalprobe 12, a second axial probe 214 located proximate a second horizontalprobe 14, and an end probe 211 located at an axial end of shaft 20. Inan embodiment, first axial probe 212 may be axially adjacent firsthorizontal probe 12 and second axial probe 214 may be axially adjacentsecond horizontal probe 14. In one embodiment, first axial probe 212 maybe located about 1 inch axially distant from first horizontal probe 12and second axial probe 214 may be located about 1 inch axially distantfrom first horizontal probe 14.

Shaft 20 is connected at a first end 24 a to shaft 42 of gas turbine 40and connected at a second end 24 b to a rotatable shaft 62 of powergenerator 60. Accordingly, shaft 20 forms a portion of a simple cycleconfiguration of a power generation system in the exemplary embodimentillustrated in FIG. 2. Shaft 20 may be rotated by gas turbine machine 40and may transmit that rotation to rotatable shaft 62 of power generator60. Rotatable shaft 62 of power generator 60 may be connected to amagnet 64 which may rotate with rotatable shaft 62 (and hence with shaft20) within a stator (not shown) of power generator 60 to generateelectric power. In an embodiment, shaft 20 may include a hollow area 22and one or more passageways 26 leading to hollow area 22. A set of wires38 may extend through passageways 26 and hollow area 22 to carry signalsto and/or from a RF telemetry system 36. RF telemetry system 36 may becapable of rotating along with shaft 20 and transmits/receives signalsto/from, for example, power generator 60 through set of wires 38 orwirelessly through a transmitting antenna of RF telemetry system 36.Target monitoring system 200 may include a pair of targets 32 and 34which may be bonded on an outer surface of shaft 20 and mounted onopposite axial ends of shaft 20 at a distance ‘G’ relative to oneanother.

In an embodiment, targets 32 and 34 may be separated along the axialdirection by about 80 inches, and a respective radii of the outersurface on which targets 32 and 34 may be bonded may be about 11 andabout 22 inches, respectively. While FIG. 2 shows targets 32 and 34being bonded on the outer surface of shaft 20 at different radiirelative to one another, targets 32 and 34 may alternatively be mountedon an outer surface of shaft 20 at the same radii. In one embodiment, atleast one of targets 32 and 34 may be formed by a pair of highlyreflective tapes which are each capable of intensifying and reflecting alight signal which is incident on the tape. Each of targets 32 and 34may be aligned at the same circumferential position or becircumferentially offset from one another. Additionally, it isunderstood that shaft 20 may include two sets of targets 32, 34, whereineach set of targets 32, 34 includes at least one target 32, 34. That is,targets 32,34 may each include a plurality of targets disposedcircumferentially around shaft 20, such that the respective probes(e.g., first axial probe 212, second axial probe 214, first horizontalprobe 12, second horizontal probe 14) of target monitoring system 200may obtain data relating to targets 32 and 34, as discussed herein.

First axial probe 212, second axial probe 214, first horizontal probe 12and second horizontal probe 14 are positioned at a perpendicular anglerelative to the long axis of shaft 20. First axial probe 212, secondaxial probe 214, first horizontal probe 12 and second horizontal probe14 may be aligned in the same axial planes as targets 32 and 34,respectively. However, it may be understood that first axial probe 212,second axial probe 214, first horizontal probe 12 and second horizontalprobe 14 may not be aligned in the same axial planes as targets 32 and34, respectively, as long as first axial probe 212, second axial probe214, first horizontal probe 12 and second horizontal probe 14 remain insubstantially the same axial and radial position relative to one anotherthroughout the determining process discussed herein. That is, probe 212and probe 12 may be positioned in the same circumferential position withrespect to shaft 20, and probe 214 and probe 14 may be positioned in thesame circumferential position with respect to shaft 20. Additionally,the circumferential position of probe 212 and probe 12 may or may not bein alignment with the circumferential position of probe 214 and probe14. In one embodiment, first axial probe 212, second axial probe 214,first horizontal probe 12 and second horizontal probe 14 may consist offiber optic elements for transmitting and receiving laser light signals.

During operation, first horizontal probe 12 and second horizontal probe14 may monitor targets 32 and 34 to determine torsional displacement ofthe shaft as discussed herein. First axial probe 212, second axial probe214, and end probe 211 may monitor shaft 20, and targets 32 and 34 todetermine axial displacement (e.g., movement) of shaft 20 and target 32,34 misalignments. At no load condition first horizontal probe 12 andfirst axial probe 212 may measure a displacement of target 32 betweeneach probe 12 and 212, the ratio of this displacement to the axialdistance between probe 12 and probe 212 representing the first gradientfor misalignment of target 32. Similarly, at no load condition secondhorizontal probe 14 and second axial probe 214 may measure adisplacement of target 34 between each probe 14 and 214, the ratio ofthis displacement to the axial distance between probe 14 and probe 214representing the second gradient for misalignment of target 34. Endprobe 211 may measure axial movement of shaft 20 at load condition.During operation, a product of the gradient and the axial movement foreach target represents an amount of false twisting for that target whichmay be factored into torque and/or power output determinations forincreased accuracy.

In an exemplary embodiment according to the present invention, a thirdhorizontal probe 12 a and a fourth horizontal probe 14 a may beemployed, and positioned in a circular arc around and perpendicular tothe long axis of shaft 20 at about 180 degrees from the positions offirst horizontal probe 12 and second horizontal probe 14, respectively.Similarly, as shown in FIG. 2, first vertical probe 15 and secondvertical probe 17 may be positioned in a circular arc around the shaft20 at about 180 degrees separation from third vertical probe 15 a andfourth vertical probe 17 a, respectively. In one embodiment, as shown inFIG. 2, first horizontal probe 12, third horizontal probe 12 a, secondhorizontal probe 14 and fourth horizontal probe 14 a are positioned with90 degrees of separation relative to one another in the same circularaxial planes as the first vertical probes 15, third vertical probe 15 a,second vertical probe 17, and fourth vertical probe 17 a, respectively.

Probes 12, 12 a, 14, 14 a, 15, 15 a, 17, 17 a, 211, 212, and 214, mayinclude laser light probes and may each be connected to a processor 10.More specifically, probes 12, 12 a, 14, 14 a, 15, 15 a, 17, 17 a, 211,212, and 214 may include at least one of a Bentley Nevada probe, aclearance probe and/or a magnetic pick-up probe. Processor 10, as willbe discussed in more detail below, is capable of calculating a torsionaldisplacement (e.g., a circumferential twist) of rotating shaft 20 basedupon measurements taken by probes 12, 12 a, 14, 14 a, 15, 15 a, 17, 17a, 211, 212, and 214, and calculating a torque imposed on shaft 20 basedon its torsional displacement. Processor 10 may include, for example,General Electric Aircraft Engine (GEAE) digital light probe system.

In an embodiment, target monitoring system 200 may include arevolutional target 33 which may be bonded to an outer surface of shaft20 and may include a metal. In one embodiment, similar to targets 32 and34, revolutional target 33 may rotate along with shaft 20. Revolutionaltarget 33 may rotate proximate a revolutional probe 13 once perrevolution of shaft 20. In an embodiment, revolutional probe 13 may be,for example, an eddy current probe which detects the presence of (metal)revolutional target 33. A signal from revolutional probe 13 may betriggered and sent to processor 10 once during every revolution of shaft20 as revolutional target 33 passes by and is detected by revolutionalprobe 13. The trigger signal provided from revolutional probe 13 enablesprocessor 10 to establish a reference zero timing for signals receivedby probe 12 and revolutional probe 13 for every revolution of shaft 20.Accordingly, a time measured from the reference zero time to the timefirst horizontal probe 12 and first vertical probe 15 receive a signalis started when revolutional probe 13 transmits a trigger signal toprocessor 10 in every revolution. In cooperation with revolutionaltarget 33, revolutional probe 13 thus forms a “one per revolutionsensor.” The operation of revolutional probe 13 and revolutional target33 may also provide information to allow processor 10 to calculate therotational speed of shaft 20. In one embodiment, the rotational speed ofshaft 20 may be determined by:w=2π(1/Δt),where Δt is the difference between two consecutive trigger signals sentfrom revolutional probe 13).

As shaft 20 rotates, first target 32 will pass once proximate probes 12,12 a, 15, and 15 a upon every revolution of shaft 20. Similarly, asshaft 20 rotates, second target 34 will pass once proximate probes 14,14 a, 17, and 17 a upon every revolution of shaft 20. The signals (e.g.,laser light signals) transmitted by probes 12, 12 a, 15, or 15 a, and14, 14 a, 17, or 17 a will be incident on targets 32 and 34,respectively, as those targets 32 and 34 pass proximate the respectiveprobes as shaft 20 rotates. Targets 32 and 34 may intensify and reflectthe transmitted signals incident on targets 32 and 34 which mayeffectively form response signals (e.g., laser light signals formed inresponse to the transmitted signals incident on targets 32, and 34) arereceived by probes 12, 12 a, 15, or 15 a, and 14, 14 a, 17, or 17 awhich may then send corresponding signals to processor 10. Processor 10may determines and record the time at which the signal reflected bytarget 32 is received by probes 12, 12 a, 15, or 15 a and the time atwhich the signal reflected by target 34 is received at probes 14, 14 a,17, or 17 a. The difference between the respective reception times ofthe reflected signals by probes 12, 12 a, 15, or 15 a, and 14, 14 a, 17,or 17 a may then be detected. For example, a difference of time of assmall as about 10 nanoseconds may be detected.

The first horizontal probe 12, third horizontal probe 12 a, firstvertical probe 15 and third vertical probe 15 a transmit firsttransmission first and second signals and receive first horizontal firstand second responses to/from the first target 32. The first verticalprobe 15, third vertical probe 15 a, second vertical probe 17, andfourth vertical probe 17 a transmit second vertical first and secondtransmissions and receive second vertical first and second responsesto/from the second target 34.

The difference in time between the signal receptions by probes 12, 12 a,14, 14 a, 15, 15 a, 17, and 17 a may change as different levels oftorque are applied to rotating shaft 20. After processor 10 hasdetermined the difference in time, processor 10 can then determine anangular torsional displacement of shaft 20. As an example, the torsionaldisplacement measured in radians may be calculated, assuming thecircumferential positions of targets 32 and 34 on shaft 20 are the same(e.g., targets 32 and 34 are circumferentially aligned), by multiplyingΔt times w, where Δt is the time difference between the receptions ofsignals by probes (12, 12 a, 15, and 15 a) and probes (14, 14 a, 17, and17 a) and w is the rotational speed of shaft 20. The rotational speed wof shaft 20 may be determined from the operation of revolutional probe13 and revolutional target 33 as discussed above.

Signals received by laser light probes 12, 12 a, 14, 14 a, 15, 15 a, 17,and 17 a when a measurable torque is imposed on shaft 20 may vary as aresult of torsional displacement (i.e., circumferential twist). Targets32 and 34 which were previously circumferentially aligned thereforebecome circumferentially offset from one another so that the respectivesignals reflected by targets 32 and 34 are received by laser lightprobes (12, 12 a, 15, and 15 a) and laser light probes (14, 14 a, 17,and 17 a) at different times. This difference in time Δt may bemultiplied by the rotational speed of the shaft (w) to calculate thetorsional displacement in radians. Processor 10 may then calculate thetorque imposed on rotating shaft 20 based on its calculated torsionaldisplacement. In one embodiment, the torque may be calculated from thetorsional displacement using a finite element model analysis, and powergenerated by gas turbine 40 may be determined based on the calculatedtorque. In particular, torque on shaft 20 may be calculated from thetorsional displacement as follows. If shaft 20 comprises a uniformmaterial at a constant temperature and its cross-sectional area isuniform and constant over its entire length, then torque may becalculated using the closed form solution:

$\tau = \frac{(\theta)(G)(J)}{(L)}$

Where τ=torque on shaft 20, θ=torsional displacement in radians (anglechange measured by probes (12, 12 a, 15, and 15 a) and probes (14, 14 a,17, and 17 a) and calculated by processor 10), G=shear modulus of thematerial of shaft 20 (e.g., available in engineering handbooks,calculated using self-calibration), j=polar moment of inertia andL=axial distance between probes 12/12 a and 14/14 a. The polar moment ofinertia (j) is the inherent stiffness of shaft 20 and can be calculatedfor a solid circular cross section where R=radius of shaft 20, by:

$j = \frac{(\pi)\left( R^{*} \right)}{2}$

The torque calculation becomes more complex to precisely determine ifany one or more of the following occur: Shear modulus (G) changes alongthe length and/or radial direction (e.g., due to temperature changes ofthe shaft material or use of a different material), the cross-sectionalarea of shaft 20 is not uniform (e.g., keyway notch), and/or thecross-sectional area is not constant along the length of shaft 20.

While shaft 20 illustrated in the exemplary embodiment of FIG. 2 isrotated by a gas turbine 40, those skilled in the art will appreciatethat shaft 20 may alternatively be rotated by another machine such as asteam turbine, nuclear power generator or internal combustion engine.Moreover, although shaft 20 transmits the rotational force exerted on itfrom gas turbine 40 to rotate a magnet 64 in power generator 60, thoseskilled in the art will appreciate that shaft 20 can be alternativelyconnected to drive other loads. For example, shaft 20, once rotated by amachine such as turbine 40, can be used to drive other loads such asrotating a propeller on a vehicle.

FIGS. 3-4 illustrate another exemplary embodiment of the presentinvention. Reference numbers corresponding to parts previously describedfor previous embodiments will remain the same. Only the differences fromprevious embodiments will be discussed in detail. While FIG. 2illustrates shaft 20 as part of a simple cycle power generation system,FIGS. 3-4 illustrate shaft 20 as part of a combined cycle powergeneration system. Specifically, shaft 20 illustrated in FIGS. 3-4 isrotated by gas turbine 40 while steam turbine 50 imposes a rotationalforce on generator shaft 62 of power generator 60. Axial end 24 a ofshaft 20 is connected to turbine shaft 42 of gas turbine 40 and axialend 24 b of shaft 20 is connected to steam turbine shaft 52 of steamturbine 50. Gas turbine 40 rotates turbine shaft 42 to rotate shaft 20and, in turn, shaft 20 rotates steam turbine shaft 52 of steam turbine50. Thus, the torque imposed on shaft 20 by gas turbine 40 istransmitted to steam turbine shaft 52 which then imposes a torque ongenerator shaft 62. Generator shaft 62 is thus subject to the combinedrotational forces from steam turbine 50 and gas turbine 40. Magnet 64 ofpower generator 60 thus rotates as a result of rotational forcesprovided by steam turbine 50 and gas turbine 40.

As discussed in the embodiment of FIG. 2, as shaft 20 is rotated by gasturbine 40, signals transmitted from probes 12, 12 a, 15, and 15 a arereflected by targets 32 and 32 a and probes 14, 14 a, 17, and 17 a arereflected by targets 34 and 34 a, respectively, as they revolve and passunderneath probes 12, 12 a, 14, 14 a, 15, 15 a, 17, and 17 a. Thesignals reflected from targets 32, 32 a, 34 and 34 a are received byprobes 12, 12 a, 14, 14 a, 15, 15 a, 17, and 17 a and their respectivetimes of arrival are measured. Processor 10 then calculates thedifference in the time at which signals are received by probes 12, 12 a,14, 14 a, 15, 15 a, 17, and 17 a to determine a torsional displacementand then determines a torque imposed on shaft 20 based upon itstorsional displacement. Power generated by gas turbine 40 can becalculated from the determination of torque.

As shaft 20 twists when it is loaded, targets 32 and 34 will bedisplaced from one another as discussed above. These targets 32 and 34will also be displaced from one another if shaft 20 vibrates. Thedisplacement from shaft vibration can be measured through the use ofadditional targets 32 a and 34 a. By assessing the time of arrival of atleast one of the sets of targets 32 and 32 a (or 34 and 34 a) within onerevolution of shaft 20 and comparing it to the expected time of arrivalbased on the actual distance between the targets 32 and 32 a and therotational speed of shaft 20, the displacement from vibration can becalculated. For example, if targets 32 and 32 a are circumferentiallyoffset from one another by 180 degrees. (see FIG. 6), the respectivetimes of arrival of signals detected by probe 12 may be expected to beone-half of the time required for one complete rotation. The time for acomplete rotation may be determined through the operation ofrevolutional probe 13 and revolutional target 33 as discussed above. Thedisplacement of shaft 20 due to its vibration may then be determined bythe difference between the expected time difference and the actual timedifference that respective response signals from targets 32 and 32 a aredetected by probes 12 and/or 12 a and/or the difference between theexpected time difference and the actual time difference that respectiveresponse signals from targets 34 and 34 a are detected probe 14 and/or14 a. The total torsional displacement may thus be determined by addingthe displacement caused by the vibration and the load displacement(i.e., the torsional displacement caused by the rotational force imposedon shaft 20). Accordingly, by bonding additional targets 32 a and/or 34a to shaft 20 and detecting response signals therefrom utilizing probes12, 12 a, 14, and/or 14 a, a correctional value may be determined forthe torsional displacement resulting from the rotational force imposedon shaft 20. Accuracy in the torsional displacement measurement maytherefore be enhanced.

In this embodiment, torque 27 may cause shaft 20 to torsionally and/oraxially displace along an axial length of shaft 20 causing a second end23 of shaft 20 (shown in phantom) to move axially and/or radiallyrelative to a first end 25 of shaft 20. As can be seen, second end 23may displace proportionally relative to torque 27 in a radial direction.A set of targets disposed about shaft 20 may also be displaced by thistorsional displacement creating a difference between a set of probes onfirst end 25 and second end 23.

Turning to FIG. 7, a schematic view of a target monitoring system 200disposed about a shaft 20 is shown according to embodiments of theinvention. In this embodiment, target monitoring system 200 includes afirst horizontal probe 12 and a first axial probe 212 located proximateshaft 20 and target 32. First horizontal probe 12 and first axial probe212 are located a first predetermined axial distance ‘d₁’ apart from oneanother. In an embodiment, d₁₋₂ may be an axial distance relative toshaft 20. In one embodiment, first predetermined axial distance d₁ maybe about 3 centimeters (cm). As a result of distance d₁, firsthorizontal probe 12 and first axial probe 212 may have unique sightlines (shown in phantom) to target 32. These unique sidelines may enableprocessor 10 to determine a first offset Δh₁ between probes 12 and 212which may be used to determine a first gradient for target 32.Similarly, a second axial probe 214 and a second horizontal probe 14 maybe used to determine a second gradient for a target 34 located proximatea second end 224 of shaft 20. More specifically, as shown in FIG. 7,second horizontal probe 14 and second axial probe 214 are located asecond predetermined axial distance ‘d₂’ apart from one another. In anembodiment, as shown in FIG. 7, second predetermined axial distance d₂may be substantially equal to first predetermined axial distance d₁(e.g., about 3 cm). However, it may be understood that firstpredetermined axial distance d₁ and second predetermined axial distanced₂ do not need to be substantially equal, as long as first predeterminedaxial distance d₁ and second predetermined axial distance d₂ remainconstant during the determining process discussed herein. These uniquesidelines may enable processor 10 to determine a second offset Δh₂between probes 14 and 214 which may be used to determine a secondgradient for target 34. The first gradient for target 32 and the secondgradient for target 34 may be compared and the magnitude of anydifference between the gradients may be used to calculate a differencebetween torque reported without respect to the gradients and actualtorque. This calculated difference, due to the difference between thegradients, may be used to correct the reported torque measurement.Target monitoring system 200 further includes end probe 211 which isdisposed proximate a first end 222 of shaft 20 and is configured tomonitor axial movement of shaft 20 during operation.

First predetermined axial distance d₁ and second predetermined axialdistance d₂ may be determined prior to operation of turbine 2 (FIG. 1).Additionally, during operation of turbine 2 (FIG. 1) and targetmonitoring system 200, signals from probes 12, 212, 14 and 214,respectively, are measured. Processor 10, receiving signals from probes12, 212, 14 and 214, respectively, may then calculate first offset Δh₁for target 32 and second offset Δh₂ for target 34. Processor 10 maysubsequently calculate the gradients for each respective target 32, 34,relating to the measured axial movement discussed herein, by:

${Gradient} = \frac{\Delta\; h}{d}$

Turning to FIG. 8, a target control system 500 is shown including afirst target 232 and a fifth target 234 communicatively connected to acomputing device 510 and a shaft 20 according to embodiments of theinvention. Target control system 500 includes a computer infrastructure502 that can perform the various processes described herein. Inparticular, computer infrastructure 502 is shown including computingdevice 510 which includes a target displacement system 507, whichenables computing device 510 to monitor shaft 20 and targets 232 and 234via probes 12, 14, 211, 212, and 214, and analyze and/or predictdisplacements and/or movements of portions of shaft 20 by performing theprocess steps of the disclosure. In an embodiment, computing device 510may determine a set of gradients for first target 232 and second target234 during non-load conditions and then determine axial movement ofshaft 20 during operation via end probe 211. Computing device 510 maythen determine a product of the gradient for each device and the axialmovement of shaft 20 and factor this product into torque and/or poweroutput determinations. In one embodiment, computing device 510 maydetermine a displacement between a first end of shaft 20 and a secondend of shaft 20. Target control system 500 may be operated manually by atechnician, automatically by computing device 510, and/or in conjunctionwith a technician and computing device 510.

As previously mentioned and discussed further below, target displacementsystem 507 has the technical effect of enabling computing device 510 toperform, among other things, the displacement and/or shaft movementmonitoring, adjustment and/or regulation described herein. It isunderstood that some of the various components shown in FIG. 8 can beimplemented independently, combined, and/or stored in memory for one ormore separate computing devices that are included in computing device510. Further, it is understood that some of the components and/orfunctionality may not be implemented, or additional schemas and/orfunctionality may be included as part of target displacement system 507.

Computing device 510 is shown including a memory 512, a processor unit(PU) 514, an input/output (I/O) interface 516, and a bus 518. Further,computing device 510 is shown in communication with an external I/Odevice/resource 520 and a storage system 522. As is known in the art, ingeneral, PU 514 executes computer program code, such as thermalmanagement system 507, that is stored in memory 512 and/or storagesystem 522. While executing computer program code, PU 514 can readand/or write data, such as graphical user interface 530 and/oroperational data 532, to/from memory 512, storage system 522, and/or I/Ointerface 516. Bus 518 provides a communications link between each ofthe components in computing device 510. I/O device 520 can comprise anydevice that enables a user to interact with computing device 510 or anydevice that enables computing device 510 to communicate with one or moreother computing devices. Input/output devices (including but not limitedto keyboards, displays, pointing devices, etc.) can be coupled to thesystem either directly or through intervening I/O controllers.

In some embodiments, as shown in FIG. 8, target control system 500 mayinclude set of probes 12, 14, 211, 212, and 214 communicativelyconnected to shaft 20 via targets 232 and 234, and communicativelyconnected to computing device 510 (e.g., via wireless or hard-wiredmeans). Targets 232 and 234 may obtain a set of operational data 532(e.g., displacements, locations, distances, etc.) and transmitoperational data 532 to computing device 510 for processing with targetdisplacement system 507 as a part of torque and/or output determinationcalculations. In one embodiment, computing device 510 may include systemdata 536 (e.g., distances between targets, a length of shaft 20, ametallurgical composition of shaft 20, etc.) and a graphical userinterface 530 for display of measurements and calculations to atechnician.

In any event, computing device 510 can comprise any general purposecomputing article of manufacture capable of executing computer programcode installed by a user (e.g., a personal computer, server, handhelddevice, etc.). However, it is understood that computing device 510 isonly representative of various possible equivalent computing devicesand/or technicians that may perform the various process steps of thedisclosure. To this extent, in other embodiments, computing device 510can comprise any specific purpose computing article of manufacturecomprising hardware and/or computer program code for performing specificfunctions, any computing article of manufacture that comprises acombination of specific purpose and general purpose hardware/software,or the like. In each case, the program code and hardware can be createdusing standard programming and engineering techniques, respectively. Inone embodiment, computing device 510 may be/include a distributedcontrol system.

Turning to FIG. 9, a schematic view of portions of a multi-shaftcombined cycle power plant 900 is shown. Combined cycle power plant 900may include, for example, a gas turbine 980 operably connected to agenerator 970. Generator 970 and gas turbine 980 may be mechanicallycoupled by a shaft 915, which may transfer energy between a drive shaft(not shown) of gas turbine 980 and generator 970. Also shown in FIG. 9is a heat exchanger 986 operably connected to gas turbine 980 and asteam turbine 992. Heat exchanger 986 may be fluidly connected to bothgas turbine 980 and a steam turbine 992 via conventional conduits(numbering omitted). Gas turbine 980 and/or steam turbine 992 mayinclude target monitoring system 200 of FIG. 7 or other embodimentsdescribed herein. Heat exchanger 986 may be a conventional heat recoverysteam generator (HRSG), such as those used in conventional combinedcycle power systems. As is known in the art of power generation, HRSG986 may use hot exhaust from gas turbine 980, combined with a watersupply, to create steam which is fed to steam turbine 992. Steam turbine992 may optionally be coupled to a second generator system 970 (via asecond shaft 915). It is understood that generators 970 and shafts 915may be of any size or type known in the art and may differ dependingupon their application or the system to which they are connected. Commonnumbering of the generators and shafts is for clarity and does notnecessarily suggest these generators or shafts are identical. In anotherembodiment, shown in FIG. 10, a single shaft combined cycle power plant990 may include a single generator 970 coupled to both gas turbine 980and steam turbine 992 via a single shaft 915. Steam turbine 992 and/orgas turbine 980 may include target monitoring system 200 of FIG. 7 orother embodiments described herein.

Although discussed herein as being utilized within power generationsystems (e.g., gas turbine systems), it is understood that targetmonitoring system 200 may be utilized by system or component utilizing ashaft for power transmission. For example, target monitoring system 200may be utilized by systems including, but not limited to: powergeneration systems, ship propulsion systems, aircraft propulsionsystems, etc.

Additional details for this invention may be found in U.S. Pat. No.7,415,363.

The apparatus and devices of the present disclosure are not limited toany one particular engine, turbine, jet engine, generator, powergeneration system or other system, and may be used with other aircraftsystems, power generation systems and/or systems (e.g., combined cycle,simple cycle, nuclear reactor, etc.). Additionally, the apparatus of thepresent invention may be used with other systems not described hereinthat may benefit from the shaft displacement and/or movement monitoringof the apparatus and devices described herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A target monitoring system comprising: a firsthorizontal probe located radially outboard of a shaft andcommunicatively connected to at least one first horizontal targetconnected to the shaft, the at least one first horizontal targetdisposed proximate a first end of the shaft; a first axial probe locatedaxially adjacent to the first horizontal probe and communicativelyconnected to the at least one first horizontal target; a secondhorizontal probe located radially outboard of the shaft communicativelyconnected to at least one second horizontal target connected to theshaft, the at least one second horizontal target disposed proximate asecond end of the shaft; a second axial probe located axially adjacentto the second horizontal probe and communicatively connected to the atleast one second horizontal target; an end probe disposed proximate thefirst end of the shaft, the end probe configured to monitor axialmovement of the shaft; and a computing device communicatively connectedto the end probe and each of the first horizontal probe, the first axialprobe, the second horizontal probe and the second axial probe, whereinthe computing device is configured to: determine a first gradient forthe at least one first horizontal target based on a displacement betweenthe first horizontal probe and the at least one first horizontal targetand the first axial probe and the at least one first horizontal target;and determine a second gradient for the at least one second horizontaltarget based on a displacement between the second horizontal probe andthe at least one second horizontal target and the second axial probe andthe at least one second horizontal target.
 2. The target monitoringsystem of claim 1, wherein the end probe includes at least one of: aBentley Nevada probe, a clearance probe and a magnetic pick-up probe. 3.The target monitoring system of claim 1, wherein at least one of thefirst horizontal probe, the first axial probe, the second horizontalprobe, and the second axial probe include an optical probe.
 4. Thetarget monitoring system of claim 1, wherein the first horizontal probeand the first axial probe are located a predetermined distance apart inthe axial direction relative to the shaft.
 5. The target monitoringsystem of claim 1, wherein the computing device is configured todetermine misalignment between the at least one first horizontal targetand the at least one second horizontal target based on the axialmovement of the shaft and the first gradient and the second gradient ofthe at least one first horizontal target and the at least one secondhorizontal target.
 6. The target monitoring system of claim 1, furthercomprising a plurality of targets disposed circumferentially about theshaft and communicatively connected to at least one of: the firsthorizontal probe, the first axial probe, the second horizontal probe,and the second axial probe.
 7. The target monitoring system of claim 6,further comprising a plurality of probes communicatively connected tothe plurality of targets and the computing device, the computing devicefurther configured to monitor the plurality of targets during rotationof the shaft via the plurality of probes, wherein the computing deviceis configured to determine torsional displacement of the shaft based onthe monitoring of the plurality of targets, and wherein the computingdevice is configured to factor axial movement of the shaft in thetorsional displacement determination.
 8. A method comprising:determining a first primary displacement between a first horizontalprobe and at least one first target on a shaft, the at least one firsttarget located proximate a first end of the shaft; determining a secondprimary displacement between a first axial probe and the at least onefirst target; calculating a first gradient of the at least one firsttarget based on the first primary displacement and the second primarydisplacement; monitoring axial movement of the shaft via an end probe;and determining an amount of false twisting of the shaft at loadcondition based on: a difference between the first gradient and acalculated second gradient; and the axial movement of the shaft.
 9. Themethod of claim 8, further comprising: determining a first secondarydisplacement between a second horizontal probe and at least one secondtarget on the shaft, the at least one second target located proximate asecond end of the shaft; determining a second secondary displacementbetween a second axial probe and the at least one second target; andcalculating the second gradient of the second target based on the firstsecondary displacement and the second secondary displacement.
 10. Themethod of claim 8, wherein the shaft is at a no load condition duringthe determining of the first displacement and the determining of thesecond displacement.
 11. The method of claim 8, wherein the shaft is ata load condition during the monitoring of the axial movement.
 12. Themethod of claim 8, wherein the end probe includes at least one of: aBentley Nevada probe, a clearance probe and a magnetic pick-up probe.13. The method of claim 8, wherein the first horizontal probe and thefirst axial probe are located a predetermined distance apart in theaxial direction relative to the shaft.
 14. The method of claim 8,wherein at least one of the first horizontal probe, the first axialprobe, the second horizontal probe, and the second axial probe includean optical probe.
 15. The method of claim 8, further comprising:monitoring via a computing device a plurality of probes communicativelyconnected to a plurality of targets disposed on the shaft, the computingdevice configured to monitor the plurality of targets during rotation ofthe shaft via the plurality of probes, wherein the computing device isconfigured to determine torsional displacement of the shaft based on themonitoring of the plurality of targets, and wherein the computing deviceis configured to factor axial movement of the shaft in the torsionaldisplacement determination.
 16. A turbine comprising: a stator; aworking fluid passage substantially surrounded by the stator; and ashaft configured radially inboard of the stator and in the working fluidpassage; and a target monitoring system communicatively connected to theshaft and configured to monitor displacement of the shaft duringoperation of the turbine, the target monitoring system including: afirst horizontal probe located radially outboard of the shaft andcommunicatively connected to at least one first horizontal targetconnected to the shaft, the at least one first horizontal targetdisposed proximate a first end of the shaft; a first axial probe locatedaxially adjacent to the first horizontal probe and communicativelyconnected to the at least one first horizontal target; a secondhorizontal probe located radially outboard of the shaft communicativelyconnected to at least one second horizontal target connected to theshaft, the at least one second horizontal target disposed proximate asecond end of the shaft; a second axial probe located axially adjacentto the second horizontal probe and communicatively connected to the atleast one second horizontal target; an end probe disposed proximate thefirst end of the shaft, the end probe configured to monitor axialmovement of the shaft; and a computing device communicatively connectedto the end probe and each of the first horizontal probe, the first axialprobe, the second horizontal probe and the second axial probe, whereinthe computing device is configured to: determine a first gradient forthe at least one first horizontal target based on a displacement betweenthe first horizontal probe and the at least one first horizontal targetand the first axial probe and the at least one first horizontal target;and determine a second gradient for the at least one second horizontaltarget based on a displacement between the second horizontal probe andthe at least one second horizontal target and the second axial probe andthe at least one second horizontal target.
 17. The turbine of claim 16,wherein the end probe includes at least one of: a Bentley Nevada probe,a clearance probe and a magnetic pick-up probe.
 18. The turbine of claim16, wherein at least one of the first horizontal probe, the first axialprobe, the second horizontal probe, and the second axial probe includean optical probe.
 19. The turbine of claim 16, wherein the firsthorizontal probe and the first axial probe are located a predetermineddistance apart in the axial direction relative to the shaft.
 20. Theturbine of claim 16, wherein the computing device is configured todetermine misalignment between the at least one first horizontal targetand the at least one second horizontal target based on the axialmovement of the shaft and the first gradient and the second gradient ofthe at least one first horizontal target and the at least one secondhorizontal target.